Why do I have on and off feelings for my boyfriend?

we have been dating for more than a year. but during the course of our relationship, my feelings for him would be on and off. there would be times when i'd be so in to him, and other times, i'd feel annoyed or bored and it would feel like i don't even like him. he's a great guy, and he's really thoughtful, loving, caring and nice. he's also a romantic guy and he's done a lot for me. there are times when i feel he's perfect for me, because he loves me for who i am. but other times, i feel like..i'm settling too early, and haven't explored much (this is my first relationship...and i'm 19 now), and that i could find someone possibly even better. i have broken up with him once because it got to the point where i knew i just didn't like him anymore and have been mistreating him. but within less than a month, we got back together again because i missed him. i know, it sounds cliche. is this a normal thing? or is it because of our history - we did start off rocky. we had a lot of fights when we started and he would always be so demanding because i never gave him much. but that all improved over time, and of course , after the breakup and get-back-together, he's been treating me wonderfully. but i'm now back to feeling off about it and i'm not sure what to do. i know if i were to be honest with him, he would try and work it out, because he never wants the relationship to be over - he loves me a lot. and i'm not sure whether to end it because he's such a great guy to me. thoughts?